This invention regards a method of injecting solvent in a subsurface well. More particularly, it regards a method in which the solvent is directed towards the formation wall of the subsurface well by means of a releasable duct. The invention also regards a device for implementing the method.
It is common, in order to stimulate the production from a subsurface well, to inject a solvent in the well. If the well formation comprises a carbonate material, acid is often used as solvent, e.g. hydrochloric acid, HCl, at an appropriate concentration.
It is known to pump the solvent into a casing and out into the well formation via perforations in the casing. Thus Norwegian patent application no. 20034790 describes a method in which the solvent is pumped out through said perforations at a sufficient concentration and in sufficient quantity to cause the surrounding formation to collapse to a certain extent.
The drawback of prior art is that it is difficult to direct the solvent to the area of the well formation that requires treatment. The solvent may for instance follow natural fractures to areas where the introduction of these types of chemicals is not desirable. Uncontrolled inflow of the solvent may dissolve the formation around the well without effecting the formation of fractures that are deep enough to create flow paths to the reservoir.
This type of incorrect treatment of the well formation may cause e.g. a significant increase in water production from the subsurface well.